Das-triazine brighteners and paper made therewith



United States Patent 3,464,886 DAS-TRIAZINE BRIGHTENERS AND PAPER MADE THEREWITH Albert Peter Paul, Teaneck, N.J., assignor to American 1(slyanamid Company, Stamford, Conn., a corporation of awe No Drawing. Filed Apr. 29, 1966, Ser. No. 546,166 Int. Cl. D2111 3/80 US. Cl. 162162 8 Claims ABSTRACT OF THE DISCLOSURE New non-yellowing brighteners derived from 4,4'-bis (triazinylamino)-stilbene-2,2-disulfonic acid and which contain as 'a substituent of the s-triazine ring at least one bis(2-carbamoylethyl) amino moiety are valuable for whitening paper made from cellulosic fibers.

This invention relates generally to new brighteners or optical bleaching agents for paper and to an improved method for whitening paper by the use therewith during some stage of its manufacture, and more particularly, it relates to novel, selected bis-triazinylamino-stilbene compounds containing at least one iminobispropionamide radical (or bis-(2-carbamoylethyl) amino group).

The compounds of this invention which have been found to be especially useful as paper brighteners, have the general formula:

N R;[ lNH- CH= N SIOQH wherein R is 'a member selected from the group consisting of methoxy and R as defined hereinafter, and R is a bis(2-carbamoylethyl) amino group. It is also contemplated that the mono and dialkali metal, ammonium and amine salts of the compounds having the foregoing generalized formula can be used in the formulations for paper brighteners in accord with the invention.

In the past, various chemical compounds have been used as optical bleaching agents and certain optical bleaching agents of the triazinyl stilbcne type have been reported in the .art as brighteners for paper. However, these prior art compounds have one or more of the following definciencies:

(1) Some brighteners discolor the paper in the concentration in which they must be present in the paper to be effective.

(2) Some compounds have little or no affinity for cellulose of the paper, that is, they are not substantive.

(3) Others have too much afiinity; exhaust too fast thus producing feathering; they are, in effect, too substantive.

(4) Some have insufiicient or weak fluorescence when applied in or on paper.

(5) Some fluoresce too green a blue, thus giving 'a more pronounced yellow efiect to the untreated paper which is naturally yellowish.

(6) Some make paper yellow under the acid conditions involved in treatment or in the paper manufacture. They may actually dye paper yellow at low pH.

(7) Some lack usefulness over a Wide range of pH from 4 to 9. This may be due to various factors such as lack of stability, quenching of fluorescence, or yellowing, feathering and the like.

(8) Some do not have equal performance in both beater and finishing operations.

(9) Some exhibit fluorescence quenching in the presence of alum.

(10) Some are incompatible with other paper additives, fillers, resins and softeners ordinarily used in paper manufacturing.

(11) Finally, the prospective brighteners may have other physical deficencies such as poor solubility or dispersibility and the like, tending to cause feathering and so forth.

It is an object of this invention to provide :a new limited group of substituted triazine compounds especially adapted for use as paper brighteners which do not have the above listed deficiences.

It is another object to provide processes for applying these brighteners to give paper an improved chorma and brighteness efiects.

Other objects will become apparent from the more complete description of the invention presented hereinafter.

The brighteners of this invention are an improvement over brighteners of related types previously known in the art in that they give distinctive reddish-blue shades of fluorescence which makes paper appear much Whiter. They are strongly fluorescent and give a strong clear whitening effect when applied to cellulose materials and especially when used in connection with paper. They are soluble and stable under acid conditions and can be used throughout the pH range which is standard for paper manufacture. They are especially good at low pH where some other brighteners either break down or show reduced efficacy. They have aflinity for cellulose and are non-yellowing and non-feathering. They are compatible with other paper chemicals, rosin, alum, fillers, softeners, wet strength resins, dyes and the like. They can also be used to brighten or intensitfy the color of dyed papers.

These compounds are useful for whitening paper when applied to paper pulp during beater operations and in finishing by tub sizing using a size press or by calendering or coating.

The new compounds or brighteners which are the subject matter of this invention can be prepared by reacting in any order of succession, 2 moles of cyanuric chloride with 2 moles of methanol, 1 mole of 4,4-diaminostilbene-2,2'-disulfonic acid or a salt thereof, and 2 moles of an iminobis-propionamide salt. Alternatively, to obtain the species containing two bis(2-carbamoylethyl) amino groups, 2 moles of cyanuric chloride are reacted with 1 mole of 4,4-diaminostilbene-2,2'-disulfonic acid or a salt thereof and 4 moles of an iminobispropionamide salt. Preferably, the methanol, if used, should be allowed to react first.

In a typical preferred method for preparation, 2 moles of cyanuric chloride are reacted with 2 moles of methanol in the presence of sodium bicarbonate at a temperature of from about 10 C. to ambient temperatures. The reaction product is then further reacted with approximately 1 mole of 4,4-diaminostilbene-2,2'-disulfonic acid in solution at 3550 C., in the presence of sodium hydroxide. Then a solution of 2 moles of iminobispropionamide sulfate is reacted with the last chloro group of cyanuric chloride, in the presence of sodium hydroxide at 50 to C. The whole is then made slightly alkaline. This mixture may be used as a concentrated solution of brightener directly in paper manufacture, or the product may be isolated as the sodium salt, by evaporation or salting out of the product as desired.

In the preferred practice of this invention, the whitening of paper may be achieved by using 0.01 to 2% of the brightener by weight of the paper or paper pulp, but either smaller or greater concentrations may be used to give corresponding lesser or greater brightening effects as desired.

When the brighteners are used in beater application, a good white is obtained with 0.080.5% of brightener by weight of paper pulp. These novel brighteners can be added before or after the alum. They are compatible with wood rosins, fillers, such as titanium dioxide, barium sulfate, zinc sufide, calcium carbonate, silicon dioxide, starches and clay, with wet strength resins, or with softeners ad dyes. Adjustment of the pH is made with alum normally used on the basis of about 4% by weight of the paper. In conventional practice, the pH of the paper pulp mixture is adjusted to 7, or below, before the paper is formed and finished.

The brighteners of this invention may also be used in sizing operations of the paper, such as tub size or size press, in which they may be employed in starch solutions in 0.51% concentration or in other aqueous sizing formulations.

The brighteners of this invention may be used in calendering with just the brightener present in water in a concentration of 0.05 to 1% or more. By this method, the completed paper is treated with the solution of brightener to produce a clear white paper.

Further, the brighteners of this invention may be used in coating paper in the usual aqueous coating formulations which include clay-casein, clay-starch or clay-caseinstarch. In such coatings, the concentration of brightner may be 0.05-03% on the weight of the solids (clay, etc.).

These new brighteners may be used separately or in admixture with other materials for superior whitening of paper in all stages of its manufacture. They have thus been found to be very versatile in their modes of use and application.

The new brighteners of this invention may be converted to methylolated reactive brighteners which can react with cellulose fibers including cotton and paper, as well as other fibers having reactive hydrogen, such as silk, wool and nylon.

The brighteners are methylolated in aqueous solution with at least two moles of formaldehyde for each mole of iminobispropionamide group at temperatures of 2090 C., and a pH above neutrality, about pH 7.2 to 10, until methylolation is complete. Such methylol groups remain active if further methylated or acetylated.

The methylolated brightener may be applied from an aqueous pad bath at pH 4-7 containing an acid catalyst, such as magnesium or ammonium chloride, ammonium sulfate or triethanolamine hydrochloride, in an amount 10-40% by weight of the brightener. The fabric thus padded is dried and cured at 300375 F. until fixation of the dye to the fabric is complete. The fabric is then soaped, rinsed and dried. The brightener is thus chemically linked to the fiber molecules of the fabric. The fabric is brightened.

The following examples illustrate this invention. They represent, however, only specific illustrative embodiments of the invention, and it is in no way intended to limit the invention thereto.

fuomomooNHm 2 To a mixture of 18.5 g. (0.1 mole) of cyanuric chloride in 150 ml. acetone, 50 ml. methanol and 2.5 ml. water, is added, with stirring, 16.9 g. (0.20 mole) sodium bicarbonate. The mixture is stirred and heated at 2535 C. for one hour. To it is added a warm solution of 18.9 g. (0.05 mole) of 97.7% real, technical grade 4,4'-diaminostilbene-2,2-disulfonic acid in a mixture of 200 ml. acetone, 200 ml. water and 20 ml. 5 N sodium hydroxide solution. The whole mixture is heated to 50 C., and stirred at 50 C. until a test for free amine is negative.

To this mixture containing 4,4'-bis(4-chloro-6-methoxytriazin 2 ylamino)stilbene-2,2'-disulfonic acid is added a solution prepared by mixing 25.7 g. (0.10 mole) of iminobispropionamide sulfate with 150 ml. water and 40 ml. 5 N sodium hydroxide solution (0.20 mole). The whole is heated, with stirring to 75 C. (reflux), and held at reflux for two hours. At the end of each hour of the two-hour period, is added 20 ml. 5 N sodium hydroxide solution.

The mixture is cooled, the product filtered and washed with 10% sodium chloride solution and dried in vaccuo. Yield 34.8 g. Its absorptivity at 347 Ill 4. is k=48.4.

EXAMPLE 2 SO Na To a mixture of 9.30 g. (0.025 mole) of 99.5% 4,4- diamino-stilbene disulfonic acid, 150ml. water, and 50 ml. acetone, there is added, with warming and stirring, 10 ml. (0.05 mole) 5 N sodium hydroxide. The resulting solution is then cooled to 0 C., and a cold solution of 9.23 g. (0.05 mole) cyanuric chloride in 125 ml. acetone added. After stirring 10 minutes at 05 C., the pH is adjusted to about 5 with 16 ml. (0.05 mole) 5 N sodium hydroxide solution. There is then added a solution of 25.73 g. (0.10 mole) of iminobispropionamide sulfate, NH(CH CH CONH H SO in 100 ml. water and 20 ml. (0.1 mole) 5 N sodium hydroxide solution. The reaction mixture is heated gradually to 70 C. to strip off the acetone, after which the pH is adjusted to about 5 with 5 N sodium hydroxide solution. The mixture is heated to C. and held at 90 C. for one hour. A solution of 5 N sodium hydroxide solution is then added to make the mixture strongly basic. The whole is then cooled and the product filtered. The product is slurn'ed in acetone, filtered, washed with acetone and dried in vaccuo over potassium hydroxide. The yield is 20.72 g. of product. Its absorptivity at 348 mg is k=45.8.

EXAMPLE 3 Beater dyeing of paper pulp To 4 g. bleached sulfite paper pulp in ml. Water is added 0.5 ml. of a 4% solution of alum. The pH is adjusted to 4.5 with 4% alum solution, if necessary.

An 0.1% solution of the brightener is added as follows, based on the absorptivity (k) values of the products of Examples 1 and 2, respectively: (a) 3.3 ml. of a 0.1% solution of the product of Example 1 or ('b) 3.5 ml. of a 0.1% solution of the product of Example 2.

The whole is stirred 10 minutes. To it is added 1.0 ml. of a 4% solution of light wood rosin followed by stirring for 10 minutes. The pH is readjusted to 4.5 with 4% alum solution (about 1 ml.) and stirring continued for ten minutes.

The pulp mixture is formed into a sheet on a Williams mold, using water adjusted to, pH 4.5. The sheet is pressed at 18-20 lb. per square inch, for 30 seconds. It is dried on a drum dryer at 230240 F., for 5 minutes and conditioned at least 30 minutes at ambient humidity.

Each sheet is observed under ultraviolet light, (U.V. light) and the amount of fluorescence and chroma noted. The compounds of Examples 1 and 2 both show strong blue-white fluorescence compared to little or no fluorescence of untreated paper. In addition, both show good chroma.

Each sheet is then observed under north daylight. Under such light a hue difference is discernible to the trained eye. The sheet of Example 1 is redder than the sheet of Example 2. Both brighteners are redder than the brighteners of the art shown in Table I below. This redness is especially desirable in paper. Both sheets show a 6 clean and bright white compared to untreated paper, What is claimed is: which by contrast appears as a dull yellowish tint. 1. A compound of the formula:

A comparison of the sheets prepared above with sheets N of two very common prior art compounds similarly pre- -f N @OH= pared, are shown in Table I. l I

5 N N sour EXAMPLE 4 wherein R is a member selected from the group con- To 50 ml. of 12% starch solution is "added, using 50 ml. sisting of methoxy and a bis(2-carbamoylethyl) amino Tub size (size press) application water and either 0.083 g. of the compound of Example 1 group, and R is a bis(2-carbamoylethyl) amino group; or 0.108 g. of the compound of Example 2, such amounts and salts thereof.

being equivalent and based upon the k-values. The re- 2. The compound of claim 1 in which R is a methoxy sultant 6% starch solution is adjusted to pH 7.0-7.5 group.

with 10% alum solution. The temperature is adjusted 3. The compound of claim 1 in which both R and to 120 F. R are bis(2-carbamoylethyl) amino groups.

Unsized Mohawk offset paper is coated by uniform 4. A process of brightening paper which comprises drawdown using a No. 12 wire wound equalizer rod. The applying to said paper an aqueous composition containcoated paper is dried at 200 F., for one minute and kept ing a compound of claim 1 and thereafter drying the at constant humidity for one-half hour. paper.

Compared to untreated paper, the paper coated with 5. A process according to claim 4 wherein the aqueous the compound of Example 1 or the compound of Example composition is applied to the paper during a finishing 2 looks whiter and brighter. T o the trained eye, the tint operation. has a reddish blue hue. The coating of the compound of 6. Paper consisting of cellulosic fibers containing from Example 1 is very slightly redder than the coating of the 0.001 to 0.1% by Weight of a compound of the formula:

compound of Example 2. Both coatings fluoresce in ultra- N violet light, compared to little or no fluorescence of the 11-! ]NH -CH= untreated controls and the chroma is good. L The above procedure is repeated, except that 10% V alum solution is added until a pH of 5.5 is obtained. I

Similar results are obtained by this treatment. It is at R 2 this lower PH Of that improvement CV61 tl'lfi pllOI' art wherein R is a me mber clected from the group conis pp Fhlorescence quenching, 1055 Of chroma sisting of methoxy and a bis(2-carbamoylethyl) amino a tendency to beflome greener Y at lower P 'group, and R is a bis(2-carbamoylethyl) amino group. are faults of F 1 aft P p bl'lghtenels- Both f the 7. Paper according to claim 6 having from 0.001 to brighteners of this invention perform well at pH 5.5 and 1% b i h f the compound wherein R is a methoxy do not have these faults. group A C0IT1PafiI1 0f the P p d y thls Procedure, 8. Paper according to claim 6 having from 0.001 to With tWO P Q CQITIPOImdS slmllafly P p 011 0.1% by weight of the compound wherein both R and R equal k'vallle 1S glven in Table 5 are bis(2-carbamoylethyl) amino groups.

TABLE II References Cited d t th v Hue an g ii ig fig m UNITED STATES PATENTS ifiiilfi bnghtener pH 7.0 5115.5 2,840,557 6/1958 Williams et a1. R=-N o H OH FOREIGN PATENTS i }Standard Standard.

Compound of Example 1--.. Redder, Redder, 8 14, 79 6/1959 Great Britain.

stronger. stronger. 1 1 072 /19 5 Japan 43,527 9/1960 Poland.

Sta dard Standard. R i n s. LEON BASHORE, Primary Examiner 1 Compound of Example 1. Much redder. Much redder. US. Cl. X.R.

Compound of Example 2 Slightly redder" Much Te 1 2 9 

